1. Field of the Invention
The invention relates to a device to align and mount a workpiece on a holding device. Teeth or sets of teeth are considered as workpieces, which must be aligned and mounted on the holding device for the purpose of measuring from one specific direction.
The device according to the invention is used particularly in the preparation for optical measurements of impressions or models of sets of teeth. The measurement data obtained from the measuring is further processed by dental CAD/CAM procedures. Hereby it is necessary to firmly mount models or impressions in an apparatus for optical measuring. In optical measuring one always measures from one single viewing direction or several measurements are taken from various specified viewing directions one after the other. There is an interest to keep the number of (viewing) directions to a minimum. This is achieved in that the measurement is taken from a favorable direction. It is especially advantageous during measuring of models of ready-prepared teeth and manufacturing of dentures to measure from the more recent insertion direction of the dental prosthesis that is to be produced. Measuring of the model only is sufficient in this case to obtain all important data. There is therefore the necessity to fasten the model in the measuring apparatus in such a manner that it may be measured from exactly that advantageous direction.
2. The Prior Art
EP 0 455 855 B1 discloses a method for producing medical, particularly dental prosthetic fitting bodies wherein a positive or negative model is produced. The model is subsequently inserted into a receiving device of a processing apparatus and is then measured tri-dimensional with the aid of a measuring device. Thereby it is possible that the model can be simultaneously rotated and moved linear during measuring whereby the model may be measured from various viewing directions.
It is the object of the present invention to make an accurate measurement possible even when a rotational movement of the workpiece is not desired for some reason or is not possible for the purpose of measuring. In addition, it is necessary that the workpiece to be measured on the holding device is aligned in a suitable manner so it can be later received in the measuring apparatus.
The device to align and mount a workpiece on a holding device, according to the invention, is provided with a receiving opening for the holding device whereby means for positioning relative to the receiving device are disposed on the receiving opening. The holding device is connected with a workpiece carrier. The workpiece carrier is adjustable against the holding device and there are optical means proposed for viewing of the workpiece.
With such type of a device alignment may be performed outside the measuring device of the workpiece, which is disposed on the workpiece carrier, in relation to the holding device whereby the direction of the holding device may be clearly determined. This alignment is performed according to the necessary criteria for the measurement. Should teeth be the workpiece to be measured, which are to be fitted into a fitting body, then the measurement direction is preferably the insertion direction of the fitting body.
The optical means are advantageously disposed on an axis perpendicular to the center axis of the holding device since in this case the measuring device is also designed in this manner. The axis of the optical means in relation to the holding device is preferably the same as the axis of the measurement.
Should the workpiece have recesses, then the workpiece can be aligned in such a way that measurement of a recess is made possible as long as there is no undercutting.
To avoid tilting during viewing of the workpiece by optical means, it is advantageous if at least two cooperating alignment aids are provided. Concentric circles arranged at a distance to one another along the center axis of the optical means are especially suitable as alignment aids. Of course, cross hairs of similar alignment aids may be provided here also.
As optical means are considered a magnifying lens or a telescope; however a video camera in the vicinity of the workpiece may also be provided together with a display device at a distance thereof.
Locking means for the workpiece carrier may be provided on the holding device to avoid unintentional displacement of the workpiece carrier relative to the holding device.
These locking means may consist of a spring chuck disposed on the holding device and a ball pivot attached to the workpiece carrier. Alternatively, the locking means could comprise two concentric conical surfaces, which would be disposed on one hand on the holding device on the other hand on the workpiece carrier. In this case, adjustment means are provided for loosening and tightening of the two conical surfaces.
The holding device is preferably provided with a shank wherein the device""s locking means are arranged in such a manner that they may be accessed from the side opposite the clamping location.
In an additional embodiment, the workpiece carrier is provided with a diameter-adjusting, spring-loaded stud, whereas the holding device is provided with a receiving opening for the stud and wherein the stud is pressed together by its spring action in relation to its diameter in the installed condition. Thereby a friction lock is obtained, which prevents unintentional pivoting.